(1) Field of the Invention
The present invention relates to the formation of sugar acetals or ketals as a means for the separation of the pentoses, xylose and arabinose from mixtures of saccharides. In particular, the present invention relates to the separation of the pentoses from lignocellulosic materials which have been hydrolyzed. The present invention further relates to the separation of xylose and arabinose from each other and to the selective recovery of arabinose from a mixture of monosaccharides, oligosaccharides and polysaccharides.
(2) Description of the Related Art
The batch and continuous recovery of cyclic acetals or ketals of polyols without a heterocyclic ring structure by distillation of mixtures of acetals or ketals is illustrated by U.S. Pat. No. 5,917,059 to Bruchmann et al and U.S. Pat. Nos. 6,548,681 B1 and 6,713,640 B2 to Miller et al. These processes are relatively straight forward but do not involve pentose isomers.
There is a need for a simpler and more economic process for producing the pentoses, xylose and arabinose, particularly from natural cellulosic sources. While the sugars can be digested with enzymes, the separation of the resulting monosaccharides is a problem which needs to be solved.